The invention relates to an arrangement for pneumatic false-twist spinning having a drafting frame with drafting rollers, having at least two air nozzles arranged behind on another in the travel path of the yarn, a yarn withdrawal device and a transfer device for transferring the movably held air nozzles from an operating position following a pair of delivery rollers of the drafting roller device to a piecing position that is offset with respect to the pair of delivery rollers.
Reference is made to our invention described and claimed in U.S. application, Ser. No. 105,813, filed on Oct. 8, 1987, based on German priority application No. 36 34 464.8 filed in Germany on Oct. 9, 1986. This other application relates to a piecing process and arrangement.
In the case of a known arrangement of the initially mentioned type, German Published Unexamined patent application (DE-OS) No. 34 11 577, that has only one air nozzle, this air nozzle, by means of a shifting motion on a guide device extending in parallel to the shafts of the drafting rollers can be brought into a piecing position. In this piecing position, a yarn that is withdrawn from the spool is guided back through the air nozzle which subsequently is moved back into its operating position. The returned yarn is placed in the pair of delivery rollers of the drafting roller device that is then started just like the withdrawal device, whereby the yarn, together with the newly supplied sliver, is introduced into the air nozzle. In the case of this construction, a coordination with the starting of the drawing roller means with respect to time is required, on the one hand, while, on the other hand, the newly supplied fiber moves directly into the air nozzle and is tied into the yarn. The danger exists in this case that the starting part of the entering sliver has not yet been drawn or drafted correctly so that thick points may be created that may lead to a clogging of the air nozzle.
It is also known from Japanese Patent Application (JP-OS) No. 61-6322 to arrange two air nozzles that are combined to a structural unit so that they can be shifted on a slideway in parallel to the shafts of the drafting rollers. A suction pipe is integrated into the slideway that, in the operating position, takes in the outgoing air of the first air nozzle. In the piecing position, the opening for the outgoing air between the air nozzles is closed off by the slideway.
In the case of another known arrangement from Japanese Patent Application (JP-OS) No. 57-89623, the air nozzles that are combined to a structural unit can be swivelled around a shaft that can be swivelled in parallel to the shafts of the drafting roller device. The air nozzles can be swivelled in such a way that they can be swivelled into a piecing position in which the inlet opening of the air nozzle that is first in the yarn travel path, is applied to a suction pipe so that a yarn that must be returned can be sucked through the air nozzles.
In the case of another known construction from Japanese Patent Application (JP-OS) No. 59-204 925, it is provided that the air nozzle can be swivelled around a shaft extending in parallel to the shafts of the drafting rollers into a piecing position in which, while the pair of delivery rollers of the drafting roller device are opened at the same time, a suction nozzle can be applied to the inlet of the air nozzles. By means of this suction nozzle, a yarn is guided back through the air nozzles and is at the same time then placed in the pair of delivery rollers of the drafting roller device.
In the case of another known arrangement from Japanese Patent Application (JP-OS) No. 61-83325, two air nozzles, in a cylindrical bore of a joint holding device, can be shifted into a piecing position, in which the compressed-air supply mean is assigned to different areas of the nozzles.
In all these constructions, there is the above-described problem, namely that a time coordination with the restarting of the drafting roller device is necessary and that the sliver that is supplied from the time of the starting of the drafting roller device is already tied into the yarn that may possibly not have been drawn or drafted correctly.
An objective of the invention to develop an arrangement of the initially mentioned type in such a way that during a piecing process, a time coordination with the starting of the drafting roller device is not required, in which case it is ensured at the same time that only a sliver that was drawn correctly in the drafting roller device is supplied to the air nozzles and tied into the yarn.
This objective is achieved according to the invention by assigning to the drafting roller device a movably held withdrawal tube that can be applied by an adjusting arrangement to the pair of delivery rollers of the drafting roller device when the air nozzles are moved out of the operating position.
By means of this development, it is possible to restart the drafting roller device before the actual piecing process so that the piecing is carried out while the drafting roller device is already operating. The sliver that had been supplied immediately before the piecing process and may not be drafted or drawn correctly is sucked off by means of the suction tube and is not tied into the yarn. It is only the sliver that is supplied continuously by the drafting roller device after the air nozzles were returned to the operating position that is tied into the yarn. It is contemplated in certain embodiments, before the piecing, to return a yarn through the air nozzles that is withdrawn after the air nozzles were moved back into the operating position and that then connects itself with the newly supplied sliver. However, embodiments are also contemplated where piecing is accomplished without the guiding-back of a spun yarn, in that the sliver, that was furnished after the air nozzles were returned into their operating position, is sucked through the air nozzles, is subsequently placed in the withdrawal device and is then transferred to a wind-on device.
In a further development of certain preferred embodiments of the invention, it is provided that means are provided for the joint transferring of the air nozzles and of the suction tube into the piecing position. In an advantageous development, it is further provided that the means for the joint transfer contain a driving or triggering element that is controlled by a yarn guard. In the case of a yarn breakage, the air nozzles and the suction tube therefore automatically arrive in the piecing position.
In order to avoid losses of fiber material after a yarn breakage, after which a certain time period elapses until the piecing takes place, it is provided that means are provided for the interruption of the supply of the drafting roller device that are controlled by a yarn guard.
In a further development of certain preferred embodiments of the invention, it is provided that for the transfer of the air nozzles and of the suction tube into the piecing position and for the interruption of the supply of the drafting roller device, an adjusting mechanism is provided that contains a joint actuating element that is controlled by a yarn guard. As a result, in the case of a yarn breakage, the arrangement is transferred automatically into the piecing position In order to be able to carry out a piecing while the drafting roller device is already operating, it is provided in a further development of the invention that the adjusting mechanism is designed in such a way that at least the supply of the drafting roller device can start operation in the piecing position of the air nozzles.
In a further development of certain preferred embodiments of the invention, it is provided that to two adjacent drafting roller device that are equipped with twin pressure rollers, two rows of in each case at least two air nozzles and a joint withdrawal device for a double end are assigned, in which case all air nozzles are arranged on a joint holding device. This arrangement is particularly useful for producing only prestrengthened ends which, however, do not yet have the strength of a yarn. The prestrengthening is therefore only carried out to such an extent that these ends that are guided together to form a double end can be wound onto a spool. Subsequently, this spool is supplied to a twisting machine or the like whereby the yarn gains its final strength. In the case of an arrangement of this type, the use of two suction pipes is advantageous, i.e., of one suction pipe for each drafting roller device because then the piecing can be carried out from operating the drafting roller device in which case no yarn must be supplied back.
In a further development of certain preferred embodiments of the invention, it is provided that the two rows of air nozzles approach one another in a V-shape in the travel direction of the yarn. As a result, the guiding-together of the yarns into a double end is carried out at least partially already in the area of the air nozzles.
In an advantageous development of certain preferred embodiments of the invention, it is provided that a bifurcated guiding element is connected behind the air nozzles of both rows, said guiding element containing the guiding ducts that are assigned to the two rows, which guiding ducts leading out into a joint connecting surface. As a result, it is possible to suck off simultaneously by means of a joint suction tool the air nozzles of both rows for a piecing in which the sliver entering at both drafting roller device is used without a returned yarn.
In order not to interfere with the sucking off of the newly supplied slivers, it is provided in a further development of certain preferred embodiments of the invention that between the outlet of the last air nozzle of each row and the bifurcated guiding element, guiding elements having guiding ducts are arranged. As a result, closed air ducts can be created through which the suction air flow is also transmitted securely. For the same purpose, adjustable cover elements are provided in a further development of certain preferred embodiments of the invention in order to at least partially close gaps between the air nozzles and/or the guiding elements.
In a further development of certain preferred embodiments of the invention, it is provided that the holding device is provided with two groove-type guides that extend in the travel path of the yarn and into which the air nozzles and/or the guiding elements are inserted. As a result, it is possible to provide the arrangement in the area of the air nozzles with a smooth closed front.
In order to permit a servicing that exceeds the operations of the normal piecing process and, for example, includes a cleaning and/or exchanging of air nozzles, it is provided in a further development of certain preferred embodiments of the invention that the holding device can be moved from the piecing position into a servicing position. In this servicing position, the essential elements will then be easily accessible. In this case, it is possible to carry out the movement into the servicing position as a continuation of the movement that takes place from the operating position into the piecing position, or to carry out a movement that deviates from it with respect to the direction and/or the type. It is, for example, contemplated to carry out the change-over into the piecing position as well as the change-over into the servicing position as swivel movements around a joint shaft. It is, however, also contemplated in certain embodiments of to provide different shafts for the two movements that are to be carried out as swivel movements, the shafts extending, for example, in planes that are directed perpendicularly with respect to one another. It is also contemplated in certain embodiments, particularly for the movement into the piecing position, to carry out a linear movement by means of which only the distance between the inlet opening of the air nozzles and the drafting roller device is increased, while the movement into the servicing position is carried out as a swivel movement.
In a further development of certain preferred embodiments of the invention, it is provided that the holding device has a plate-shaped design and, on the back side, is provided with a holding device for holding the air nozzles and/or the guiding elements and/or with means for the supplying of compressed air to the air nozzles. In this case, it is particularly advantageous if the holding device can be swivelled around a horizontal shaft into the servicing position in which it has an approximately horizontal position. In this case, the back side will be accessible from above in the manner of a table top or a work top.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.